1996 Jeep Grand Cherokee Laredo - ticking/clicking sound - shaking

Hello everyone...My name is Jeff and I am, unfortunately,
vehicle-maintenance impaired.

OK, I have a 1996 Jeep Grand Cherokee Laredo, V8. 101,000 miles on it.

Problem Description:
About a week ago, I noticed a very subtle shaking to the car as I was
driving on the highway (I drive an hour to and an hour back from work). We
have been having some bad weather (windy) of late, so I thought it was just
the wind shaking the car or, because I only noticed it on the highway, I
thought it was just the roads on the turnpike might be lumpy.

This morning, as I got off the highway, and closer to work, the shaking was
very noticeable and the engine light came on.

On break I checked oil, transmission, and coolant fluids. All were fine.

As I had the hood up and the engine on (for checking the transmission
fluid) I heard a clicking/ticking sound (like what you might hear from an
electrical shock).

Looking around, I noticed a spark coming from a wire that connects to, what
I think is a spark plug (but it was not located with the other spark plugs,
more to the front, but with the same kind of wire). The spark was going
from that wire to the compartment that holds the oil.

After checking the internet, I found a couple places that state that it
could be that the wire is bad and the electrical charge is going to ground.

I then went out and checked the wire, and sure enough, it seemed distorted
and there was a crack in it. So, I moved it away from the oil compartment
and started the car. I didn't notice the spark anymore, but I still heard a
ticking/clicking sound (no noticeable pattern).

2) Could the engine light be coming on for another reason? (possibly
letting me know that the engine isn't getting enough power because the
insulation wire is going bad)

3) Could the wire problem for a sparkplug cause the engine/car to shake and
the check engine light to come on?

4) From what I have described, does anyone have an idea of what else it
might be?

5) My commute is an hour away....will it be safe to drive it home tonight,
or I am out of luck?

Thanks SOOOO much in advance for any help anyone can offer me!

jeffcravener

1) You have the 5.2Litre Chrsyler 318 Cubic Inch V-8 in that truck and the
computer system is running on an OBD II interface. You probably were
seeing arching from the "plug" wire that connects the distributor to the
coil in the engine. This also explains the ticking sound. Ignition coil
output in an automobile is between about 40-60 thousand volts so if it is
arching, you're gonna hear it. Here's a simple explaination: The coil
powers the distributor such that when the rotor spins around inside, it
makes a contact to each plug wire at a specific time thus firing that
cylinder. This is called engine timing. If that coil to distributor wire
was loose, frayed or degraded, your engine could be experiencing a loss of
power, intermittent power interruption based on jarring from bumps, etc.
Due to this, I hypothesize that the check engine light is on due to
something such as a "multiple cylinder misfire" code detected by the coil
or pickup in the distributor and sent to the pcm. I think it was 1998
that Chrysler starting installing direct ignition on these vehicles
including the ones that have the 4.0 litre I-6. This system eliminated the
distributor and changes completely over to a coil pack over each spark
plug. Direct Ignition.
** You need to have the computer scanned for DTC's and tell us where they
are. If that MIL is on, there is a reason and the computer scan will tell
us. That is the first thing to do.
Also if you have a cylinder missing due to this, YES the O2's could be
picking up raw emissions in the exhaust gasses and throwing the check
engine light too as sort of a secondary effect scenario whereas the coil to
distributor connection being loose or worn or arching.

2)I've addressed this above :mrgreen:

3)The answer is yes. The car shaking is probably due to the engine not
running on all 8 cylinders and you are running unbalanced. The light will
come on possibly for one of the reasons that I have highlighted above.

4)Without seeing it and from what you've told us, I think that I am pretty
close to the problem. Any other thoughts???

5)Check these things before leaving work. Open the hood and make sure
that the wire running from the coil to the distributor is tightly snapped
in place at the coil end and at the distributor end. Make sure the
ticking is gone and that the engine idles and acelerates smoothly and that
there is no slight vibration from a misfire. If there is not, drive it and
see if the vibration is gone and that you have plenty of power.

6) Report back :thumbs:

cmeseadoin

Thanks for taking the amount of time you did to explain it.

OK, on lunch I went and inspected the wire as much as I could, there were
three splits in it, so I bought some electrical tape (I am doubting now if
it will be enough, with as many volts as you said that wire takes) and
wrapped it around the wire where the splits were.

The ticking/clicking stopped, and I didn't see any more arcing. I drove it
around as much as I could (with the lunch time limit) and i didn't notice
any shimming/shaking. However, the check engine light was still on.

I am going to print out what you mentioned and give it to my mechanic
tonight (well, as long as I make it home).

Someone here at work mentioned that it could be oil leaking into the
engine, causing a problem with the valves?

From what you said, and what else I have been able to find on the web seems
to point to that bad wire.

jeffcravener

You're welcome!! :thumbs: I think you need to discredit anything the
person told you about the valves, LOL. You've said NOTHING here that would
lead me in the direction that your engine is having a problem mechanically
and it sounds like that person either is car illiterate or seriously
misinformed as to what the problem is. You need to explore that wire and
replace it. Now that it is not arching, drive it home and see how she
does. If all is well then problem solved. You will have to have the check
engine light cleared at the shop. They will hook up the computer, scan it
and determine the codes (I bet it points to what I previously explained)
and then clear it out. I think you've got a very simple issue going on and
it sounds like you're on the right track...at least from all I can do
online....Good luck, let me know! :thumbs:

cmeseadoin

Cmessadoin- I'll bet he will find a P0300 series random or specific
cylinder misfire

If you find that is true, go ahead and clear them since you probably fixed
the problem when you replaced the bad plug wires

Some auto parts places can read the generic OBDII codes and clear codes and
will do it at little or no charge

tbaxleyjr

Well, when I got home I inspected the wiring more carefully, and sure
enough, 6 of the wires had cracks in the coatings.

I ran to autozone and replaced all the wires (my first 'working on a
car'). IT was surprisingly EASY...I would have been very mad had I paid
someone to do that, and then found out how easy it is to do after.

When I started it up, the check engine light DIDN'T come on! I was so
happy.

So, I guess that they sometimes reset themselves?

Driving to work was great. Itm ust have been like that for quite awhile. I
had forgotten how powerful a V8 is supposed to be!!

Also, for the last couple months, my sub woofer had been 'thumping'
sporatically. It idn't do it at all today. I guess there was some kind of
feedback from the arcing going o the sub?

Thanks again for the help everyone! What I thought was a car replacing
problem, turned out to be a simple fix. thank god for the internet!!!

jeffcravener

Yep, you nailed it......plug wires are SIMPLE and yes, I would never pay
someone either. You were simply dealing with a worn out wire-set......Yes
the sub was receiving electrical impedence feedback from the fact that your
coil was arching to the engine thus to the frame and sensitive electronics
like radios and amps will pick that up, especially when it is many volts
such as from a coil. You learn something everyday don't ya. :hi:

So let me ask you......have you checked those valves out yet to make sure
they are ok.....might wanna pull the engine down like that co-worker
suggested :laughing: :laughing: I'm JUST kidding! ;-) Enjoy a smooth
V8!! :thumbs:

cmeseadoin

Oh and I forgot.....yes the check engine light is probably off because the
vehicle has been driven enough "good trips" to cause the computer to no
longer see the error condition so it has de-illuminated the MIL on the
dash. I am sure there probably is a history code in the PCM though but if
the light is off, you're fine. The pcm reads errors by determining "good
trips." In simple terms, if the computer experiences a problem from one of
the systems it sends a red flag up called a pending code. That pending
code is remembered and then the vehicle runs itself through was is call a
"trip." If that trip or set of trips commonly called cycles, depending on
how the system is made to function by the design engineers of that auto
manufacturer, comes back clean, the pending code is forgotten and erased
from memory. If the vehicles still sees an error or fault, it is called a
bad cycle or bad trip and it says to itself, hmmm better alert the driver
and therefore the MIL is close-circuited to illuminate. Now, all this and
how it works is very complex but the basics have been explained. Some
vehicles requier X amount of cycles before it will set a code.....others
set a code when it sees something bad happen. Some Check engine lights
will come on and if the problem goes away they will still stay on for
longer as the metrics that are used are more intense to make sure that the
problem is no longer there before it will shut off the light. All cars are
a little different but that is what happened here. You eliminated the
problem, a hard code was not set in the pcm, so when it cleared and the pcm
saw that, it said BYE to the light and shut it off! :-) Enjoy :thumbs:

cmeseadoin

pretty good explanation

tbaxleyjr

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